title: Noninvasive assessment of alveolar microvascular recruitment in conscious non-sedated rats.
abstract: Recruitment of alveolar microvascular reserves, assessed from the relationship between pulmonary diffusing capacity (DLCO) and perfusion (Q˙c), is critical to the maintenance of arterial blood oxygenation. Leptin-resistant ZDF fatty diabetic (fa/fa) rats exhibit restricted cardiopulmonary physiology under anesthesia. To assess alveolar microvascular function in conscious, non-sedated, non-instrumented, and minimally restrained animals, we adapted a rebreathing technique to study fa/fa and control non-diabetic (+/+) rats (4-5 and 7-11mo old) at rest and during mild spontaneous activity. Measurements included O2 uptake, lung volume, Q˙c, DLCO, membrane diffusing capacity (DMCO), capillary blood volume (Vc) and septal tissue-blood volume. In older fa/fa than +/+ animals, DLCO and DMCO at a given Q˙c were lower; Vc was reduced in proportion to Q˙c. Results demonstrate the consequences of alveolar microangiopathy in the metabolic syndrome: lung volume restriction, reduced Q˙c, and elevated membrane resistance to diffusion. At a given Q˙c, DLCO is lower in rats and guinea pigs than dogs or humans, consistent with limited alveolar microvascular reserves in small animals.
authors.affiliation: Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9034, United States.
authors.forename: Cuneyt
authors.initials: C
authors.lastname: Yilmaz
authors.forename: Dan M
authors.initials: DM
authors.lastname: Dane
authors.forename: Priya
authors.initials: P
authors.lastname: Ravikumar
authors.forename: Roger H
authors.initials: RH
authors.lastname: Unger
authors.forename: Connie C W
authors.initials: CC
authors.lastname: Hsia
mesh_terms: D000367:Age Factors; D000818:Animals; D002196:Capillaries; D003243:Consciousness / Q000502:physiology*; D004195:Disease Models, Animal; D020738:Leptin / Q000235:genetics; D008297:Male; D009765:Obesity / Q000473:pathology; D011650:Pulmonary Alveoli / Q000098:blood supply*; D011652:Pulmonary Circulation / Q000502:physiology*; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D051381:Rats; D055647:Rats, Transgenic
chemical_list: D020738:Leptin
keywords: Alveolar microangiopathy; Lung diffusing capacity; Metabolic syndrome; Obesity; Pulmonary blood flow; Type-2 diabetes mellitus